The present invention relates to a method of making a magnetic resistance element, which is employed in a magnetic head of a magnetic disc drive unit, etc.
The magnetic resistance element is capable of detecting a magnetic field by the magnetic resistance effect, and it is employed in the magnetic head of the magnetic disc drive unit, which is capable of reading high density data from a magnetic disc. These days, the disc drive units are made smaller in size but they have large capacity of memory, further high power magnetic heads are required, so the magnetic resistance elements, in which magnetic domains are controlled by ferromagnetic layers, draw engineers"" attention.
The magnetic resistance element, in which the magnetic domains are controlled by the ferromagnetic layers, is shown in FIG. 6. An insulating layer 10 is made of an insulator, e.g., alumina, silicon oxide. A first magnetizable layer 12 is formed on the insulating layer 10; a non-magnetizable layer 14 is formed on the first magnetizable layer 12; and a second magnetizable layer 16 is formed on the non-magnetizable layer 14. One of the first and the second magnetizable layers 12 and 16 is a magnetic resistance layer (MR layer), and the other is a bias layer (SAL layer). The SAl layer applies a bias magnetic field to the MR layer so as to detect magnetic data with high sensivity. The non-magnetizable layer 14 is provided between the first and the second magnetizable layers 12 and 16 as a shielding layer. A Nixe2x80x94Fe layer is employed as the MR layer; an alloy layer, which is made of two or more selected from a group of Ni, Fe, Cr, Rh, Co, etc., is employed as the SAL layer; and a layer made of Ta, Ti or Cr is employed as the non-magnetizable layer.
Planar shapes of the first magnetizable layer 12, the non-magnetizable layer 14 and the second magnetizable layer 16 are rectangular shapes; their side faces are formed into slope faces on which terminals 18 are formed; and they constitute a main part of the magnetic resistance element. The terminals 18 are formed on the slope faces of the main part. Since the terminals 18 are formed on the slope faces, the contact area between the terminals 18 and the first and the second magnetizable layers 12 and 16 can be broader, so that the resistance of the magnetic resistance element can be reduced.
A conventional method of making the magnetic resistance element is shown in FIGS. 7A-7C. In FIG. 7A, the insulating layer 10, the first magnetizable layer 12, the non-magnetizable layer 14 and the second magnetizable layer 16 are formed on a substrate, e.g., a ceramic member. The layers can be formed, in said order, by sputtering.
As shown in FIG. 6, in the case of the magnetic resistance element of the magnetic head, etc., the terminals 18 are formed on the side slope faces. Thus, a resist layer 20, which is formed into a prescribed shape, is formed on an upper face of the second magnetizable layer 16, which is the uppermost layer as a mask, then the layers are etched, with the mask of the resist layer 20, by ion milling, as shown in FIG. 7A. In FIG. 7B, the slope faces, on which the terminals 18 (FIG. C) are formed, are formed in the first magnetizable layer 12, the non-magnetizable layer 14 and the second magnetizable layer 16 by ion milling. A sectional shape of the resist layer 20 has undercut sections, namely a wider section 20a is supported by a supporting section 20b, which is narrower than the wider section 20a. When ions are radiated by ion milling, the slope faces for the terminals 18 are formed by partially shading the ion radiation by the wider section 20a; the terminals 18 can be formed on each slope face.
To form the slope faces in the first magnetizable layer 12, the non-magnetizable layer 14 and the second magnetizable layer 16 by ion milling, they are gradually etched from the second magnetizable layer 16 toward the lower layers. In an are alocated outside of the slope faces on which the terminals 18 are formed, the insulating layer 10 is exposed, so the surface of the insulating layer 10 is slightly overetched, by ion milling, so as to leave no layers on the insulating layer 10. In FIG. 7B, a symbol xe2x80x9cLxe2x80x9d stands for depth of overetching the insulating layer 10.
In the conventional method, to correctly etch the first magnetizable layer 12, the non-magnetizable layer 14 and the second magnetizable layer 16 by ion milling, the etching is stopped on the basis of the operator""s visual observation or on the basis of the time required time to completely remove the first magnetizable layer 12, which has been previously known. Therefore, overetching of the insulating layer 10 cannot be avoided so as to completely remove the first magnetizable layer 12 from the surface of the insulating layer 10.
If the insulating layer 10 is overetched after the slope faces are formed in the first magnetizable layer 12, the non-magnetizable layer 14 and the second magnetizable layer 16, the insulating materials of the insulating layer 10 are scattered and stick onto the slope faces, on which the terminals 18 are formed. In FIG. 7C, the insulating materials 10a of the insulating layer 10 stick on the slope faces, and the terminals 18 are formed thereon.
If the terminals 18 are formed on the slope faces on which the materials 10a have stuck, the magnetic resistance element has the following disadvantages: the resistance between the terminals 18 and the main part is unstable; and therefore the resistance of the magnetic resistance element must be greater.
Further, the first and the second magnetizable layers are heated while forming on the insulating layer 10, atoms of the first magnetizable layer 12 are spread in the insulating layer 10, so that magnetic characteristic of the magnetic resistance element must be worse. In the case that the first magnetizable layer 12 is the SAL layer, if the atoms of the first magnetizable layer 12 are spread in the insulating layer 10, the magnetic characteristic of the first magnetizable layer 12 is changed, and a prescribed bias magnetic field cannot be applied.
The present invention is intended to solve the above described disadvantages of the conventional magnetic resistance elements, and an object of the present invention is to provide a method of making a magnetic resistance element, which includes the MR layer, the bias layer and the non-magnetizable layer and which has a stable magnetic characteristic and high reliability.
To achive the object, the present invention has the following steps.
Namely, the method comprises the steps of: forming a first magnetizable layer, a non-magnetizable layer and a second magnetizable layer, in this order, on an insulating layer; providing a,resist layer for forming a main part of the magnetic resistance element on the second magnetizable layer; etching side faces of the first magnetizable layer, the non-magnetizable layer and the second magnetizable layer to form into slope faces by ion milling from the second magnetizable layer side; forming terminals on the slope faces; and removing the resist layer, wherein a part of the first megnetizable layer which is located outside of the slope faces is left on the insulating layer when the side faces of the first magnetizable layer, the non-magnetizable layer and the second magnetizable layer are etched by ion milling. With this method, scattering and sticking the materials of the insulating layer onto the slope faces while the etching step can be prevented, so the highly reliable magnetic resistant element can be provided.
In the method, the thickness of the first magnetizable layer may be detected by an end sensor while the first magnetizable layer, the non-magnetizable layer and the second magnetizable layer may be etched by ion milling, so that the first magnetizable layer having a prescribed thickness can be left on the insulating layer. With this method, the thickness of the first magnetizable layer, which is on the insulating layer, can be precisely controlled.
In the method, the end sensor may be capable of detecting the intensity of the light from metallic elements in the first magnetizable layer, and the ion milling may be stopped when a predetermined time is lapsed from a time point at which the end sensor detects the peak of the intensity of the light.
In the method, the thickness of the first magnetizable layer left may be about 30 xc3x85.
And, another method of the present invention comprises the steps of: forming a first magnetizable layer, a non-magnetizable layer and a second magnetizable layer, in this order, on an insulating layer; providing a resist layer for forming a main part of the magnetic resistance element on the second magnetizable layer; etching side faces of the first magnetizable layer, the non-magnetizable layer and the second magnetizable layer to form into slope faces by ion milling from the second magnetizable layer side; forming terminals, each of which is formed on the insulating layer and the slope faces; and removing the resist layer, wherein an intermediate layer, whose resistivity is greater than that of the first and the second magnetizable layers, is formed between the insulating layer and the first magnetizable layer, and wherein a part of the intermediate layer which is located outside of the main part is left on the insulating layer when the main part is etched by ion milling.
In the method, the intermediate layer may be made of a non-magnetizable material such as Ti, Ta, Cr.
In the methods, one of the first and the second magnetizable layers is an MR layer, and the other is an SAL layer.
In the method of the present invention, the magnetizable layer is left on the insulating layer when the layers are etched by ion milling, so the main part of the magnetic resistance element can be formed without sticking the insulating materials of the insulating layer onto the slope faces, on which the terminals are formed, and the magnetic resistance element having excellent magnetic characteristic and high reliability can be made. And, a magnetic resistance element having excellent magnetic characteristic can be made by providing the magnetizable layer between the insulating layer and the first magnetizable layer.